Greek Hydraulic Telegraph of Aeneas relief

A hydraulic telegraph ( el, υδραυλικός τηλέγραφος) refers to two different

semaphore Semaphore (; ) is the use of an apparatus to create a visual signal transmitted over distance. A semaphore can be performed with devices including: fire, lights, flags, sunlight, and moving arms. Semaphores can be used for telegraphy when arra ...

systems involving the use of water-based mechanisms as a

telegraph Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas p ...

. The earliest one was developed in 4th-century BC Greece, while the other was developed in 19th-century AD

Britain Britain most often refers to: * The United Kingdom, a sovereign state in Europe comprising the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands * Great Britain, the largest island in the United King ...

. The Greek system was deployed in combination with semaphoric fires, while the latter British system was operated purely by

hydraulic Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...

fluid pressure. Although both systems employed water in their sending and receiver devices, their transmission media were completely different. The ancient Greek system transmitted its semaphoric information to the receiver visually, which limited its use to line-of-sight distances in good visibility weather conditions only. The 19th-century British system used water-filled pipes to effect changes to the water level in the receiver unit (similar to a transparent water-filled flexible tube used as a level indicator), thus limiting its range to the

hydraulic pressure Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid coun ...

that could be generated at the transmitter's device.Distant Writing: A History of the Telegraph Companies in Britain between 1838 and 1868 - Non-Competitors
Distantwriting.co.uk website. Retrieved 2009-07-14 While the Greek device was extremely limited in the codes (and hence the information) it could convey, the British device was never deployed in operation other than for very short-distance demonstrations. Although the British device could be used in any visibility within its range of operation, it could not work in freezing temperatures without additional infrastructure to heat the pipes. This contributed to its impracticality.

Greek hydraulic semaphore system

Hydraulic telegraph, 4th century BC (reconstruction)

The ancient Greek design was described in the 4th century BC by

Aeneas Tacticus Aeneas Tacticus ( grc-gre, Αἰνείας ὁ Τακτικός; fl. 4th century BC) was one of the earliest Greek writers on the art of war and is credited as the first author to provide a complete guide to securing military communications. Po ...

and the 3rd century BC by the historian

Polybius Polybius (; grc-gre, Πολύβιος, ; ) was a Greek historian of the Hellenistic period. He is noted for his work , which covered the period of 264–146 BC and the Punic Wars in detail. Polybius is important for his analysis of the mixed ...

. According to Polybius, it was used during the

First Punic War The First Punic War (264–241 BC) was the first of three wars fought between Rome and Carthage, the two main powers of the western Mediterranean in the early 3rd century BC. For 23 years, in the longest continuous conflict and grea ...

to send messages between

Sicily (man) it, Siciliana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Ethnicity , demographics1_footnotes = , demographi ...

and

Carthage Carthage was the capital city of Ancient Carthage, on the eastern side of the Lake of Tunis in what is now Tunisia. Carthage was one of the most important trading hubs of the Ancient Mediterranean and one of the most affluent cities of the classi ...

. The system involved identical containers on separate hills, which are ''not'' connected to each other; each container would be filled with water, and a vertical rod floated within it. The rods were inscribed with various predetermined

code In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication ...

s at various points along its height. To send a message, the sending operator would use a torch to signal the receiving operator; once the two were synchronized, they would simultaneously open the

spigot A tap (also spigot or faucet: see usage variations) is a valve controlling the release of a liquid or gas. Nomenclature United Kingdom * Tap is used in the United Kingdom and most of the Commonwealth for any everyday type of valve, partic ...

s at the bottom of their containers. Water would drain out until the water level reached the desired code, at which point the sender would signal with his torch, and the operators would simultaneously close their spigots. Thus the length of time between the sender's torch signals could be correlated with specific predetermined codes and messages. A contemporary description of the ancient telegraphic method was provided by Polybius. In ''The Histories'', Polybius wrote:Lahanas, Michael
Ancient Greek Communication Methods
, Mlahanas.de website. Retrieved 2009-07-14.

British hydraulic semaphore system

The British civil engineer

Francis Whishaw Francis Whishaw (13 July 1804 – October 1856) was an English civil engineer. He was known for his role in the Society of Arts, and as a writer on railways. Later in life he was a promoter of telegraph companies. Life Francis Whishaw was born 1 ...

, who later became a principal in the General Telegraph Company, publicized a hydraulic telegraph in 1838 but was unable to deploy it commercially. By applying pressure at a transmitter device connected to a water-filled pipe which travelled all the way to a similar receiver device, he was able to effect a change in the water level which would then indicate coded information to the receiver's operator. The system was estimated to cost £200 per mile (1.6 km) and could convey a vocabulary of 12,000 words. The U.K.'s ''Mechanics Magazine'' in March 1838 described it as follows:Roberts, Steven
A History of Telegraph Companies In Britain Between 1838 And 1868: Whishaw's Hydraulic Telegraph
retrieved from DistantWriting.co.uk website January 8, 2013. The article concluded speculatively that the "... hydraulic telegraph may supersede the semaphore and the galvanic telegraph".

References

External links

Connected Earth
{{DEFAULTSORT:Hydraulic Telegraph History of telecommunications Telegraphy Optical communications Ancient Greek technology Ancient Greek military terminology Ancient Greek military equipment Communications in Greece Semaphore

Greek hydraulic semaphore system

British hydraulic semaphore system

See also

References

External links